Auto merge of #100748 - SparrowLii:query_depth, r=cjgillot

add `depth_limit` in `QueryVTable` to avoid entering a new tcx in `layout_of`

Fixes #49735
Updates #48685

The `layout_of` query needs to check whether it overflows the depth limit, and the current implementation needs to create a new `ImplicitCtxt` inside `layout_of`. However, `start_query` will already create a new `ImplicitCtxt`, so we can check the depth limit in `start_query`.

We can tell whether we need to check the depth limit simply by whether the return value of `to_debug_str` of the query is `layout_of`. But I think adding the `depth_limit` field in `QueryVTable` may be more elegant and more scalable.

compiler/rustc_middle/src/query/mod.rs

@@ -1309,6 +1309,7 @@ rustc_queries! {
     query layout_of(
         key: ty::ParamEnvAnd<'tcx, Ty<'tcx>>
     ) -> Result<ty::layout::TyAndLayout<'tcx>, ty::layout::LayoutError<'tcx>> {
+        depth_limit
         desc { "computing layout of `{}`", key.value }
         remap_env_constness
     }